Studies are proposed to elucidate the role of cyclic AMP in gastric secretion. The subunits of the cyclic AMP-dependent protein kinase will be further purified and characterized. The phosphorylation and dephosphorylation of proteins endogenous to gastric mucose will be studied. Attempts will be made to isolate a protein phosphatase for these phosphoproteins and to study its regulation. Effects of gastric secretagogues on adenylate cyclase and guanylate cyclase as well as cyclic nucleotide phosphodiesterase will be studied. Pepsinogen granules will be purified and their properties investigated in order to establish the mechanism of pepsinogen release. The effect of cyclic nucleotides and the cAMP-dependent protein kinase on these granules will be studied.